Servo actuators are used to provide position control in a wide variety of electro-mechanical systems. For example, servo actuators may be used in guidance systems employed in vehicles such as aircraft, watercraft, agricultural vehicles (e.g. tractors, combines, etc.), and so forth, to adjust the motion of the vehicles without ongoing human intervention. In such systems, one or more servo actuators may be provided to control movement of the vehicle along each axis of motion controlled by the system. The servo actuators drive mechanisms (e.g., control surfaces, rudders, steering linkages, etc.) to change the course of the vehicle along the axis of motion being controlled.
In autopilot systems utilized by aircraft, servo actuators may be furnished to actuate each control surface controlled by the autopilot system (e.g., ailerons, rudder, elevators, trim, and so forth). The servo actuators move the flight control surfaces of the aircraft when the autopilot system is engaged to maintain the aircraft's course and attitude. For example, in typical implementations, the servo actuators may turn a capstan to which one end of a cable is attached. The other end of the cable is then attached to a cable or mechanical linkage that moves a flight control surface of the aircraft. As the capstan is turned, the cable is wound onto or unwound from the capstan to move the control surface.
To mitigate the possibility that a single failure of a component of a servo actuator could prevent the pilot of the aircraft from controlling the flight control surfaces of the aircraft, conventional servo actuators often employ a capstan that includes a slip clutch. The slip clutch allows the capstan to slip upon application of a predetermined torque in the event that the servo actuator had failed and was seized or jammed. In this manner, the pilot can overcome the seized actuator and maintain control of the flight control surface.